Originally Posted by
Pontius Navigator
Put another way - bandwidth.
In some areas the data link from the VHF ground station may have a very low bandwidth with limited capacity and slow speed. The satellite link will have the necessary high-speed links from ground station to the main base system. All that is necessary is to ensure that the satellite bandwidth is sufficient for the maximum traffic levels.
While it would be very expensive to increase satellite bandwidth it would involve fewer agencies and be more easily achieved on an international scale than for national agencies.
Both INMARSAT and Iridium (with their Next constellation) were in the process of increasing their available bandwidth before MH370. Both will be providing broadband links to their customers in the next few years.
The customers will be the ones having to upgrade their existing SATCOM systems to obtain the increased bandwidth.
However, most transoceanic aircraft are already capable of ADS-C over SATCOM that will work on current low bandwidth systems, and all they need to alter is the reporting rate. As was recommended by the French BEA after the AF447 crash.